Seal breeding season in the Desertas Islands, Madeira

Rosa Pires, Parque Natural da Madeira
Two females and one pup interacting at the entrance of the Bufador cave.
Two females and one pup interacting at the entrance of the Bufador cave.

As a result of the campaign to monitor the monk seal breeding season in Madeira’s Desertas islands, we could confirm already the birth of two pups, a female and a male. These two, born in September/October, were monitored over 2 weeks at the entrance of Bufador cave, where a concealed lookout post was established. From here it was possible to identify the group of seals using the cave and observe their behaviour without disturbing them or influencing their natural behaviour.

With an estimated age of 1 month, the pups used to come out of the cave very frequently, but always staying near the entrance and being followed by their mothers “Tria” and “Manchada”, or by the other three females identified in the area. In total ten different seals were identified using this cave – two pups, five females, one adult male and two juveniles. On one day it was possible to observe nine of these seals.

Three females and one male at the entrance of the Bufador cave.
Three females and one male at the entrance of the Bufador cave.

A dead seal was also found at the entrance of Bufador cave – one of the juveniles. The body was already in a state of advanced decomposition, and the cause of death could not be established. However, the presence of this dead seal resulted in interesting observations of the behaviour of one of the pups. Several times we were almost on the point of entering the water to save the pup, which had invented a “nice” game in “playing dead” by being completely inactive for long moments. In fact, when we first detected the dead juvenile, this pup was following the body, which was moving with the sea current, trying to interact with her.

Additionally a pup and a female were detected in another cave, Vermelhas, suggesting a third birth. However, sea conditions did not allow us to confirm this information.

Mother with pup from the 2014 breeding season at the Desertas.
Mother with pup from the 2014 breeding season at the Desertas.

To date, four births have been detected during 2014, including two occurring before the typical breeding season, and two deaths – the juvenile mentioned above and an adult male found in Madeira.

As part of  the new EU LIFE Project [see New EU LIFE project for Madeira’s monk seals], several surveillance cameras were placed in the most important caves around the Desertas. It is hoped that these will be an important tool in monitoring the monk seal breeding season more effectively, achieving a more accurate number of births and deaths, identifying reproducing females and gaining a better understanding of the seals’ behaviour in the caves.

Portugal

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